Calculating Net Torque on Wheel Axle

In summary, the net torque about the axle of the wheel shown is -1.4 N-m in the clockwise direction, calculated by adding the individual torques and taking into account the friction torque. The force of 35N is not taken as a component in this case, as it is already tangential to the radius.
  • #1
Jam51
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0

Homework Statement


Calculate the net torque about the axle of the wheel shown in https://jigsaw.vitalsource.com/books/9781269392464/content/id/ch08fig39 . Assume that a friction torque of 0.40 m · N opposes the motion. Where F=18N (in photo).

The picture is here: http://www.webassign.net/giancoli/8-39alt.gif

Homework Equations


τ (tau) = rF

The Attempt at a Solution


Direction of the positive torque: counterclockwise direction

T1 = 28N*24cm = 6.72 N-m

T2 = -35N*12cm = -4.2 N-m

T3 = -18N*24cm = -4.32 N-m

Now you add all these torques

6.72 N-m -4.2 N-m -4.32 N-m = -1.8 N-m

Since I know the direction of rotation is clockwise, I added the friction torque to that result in the opposite direction:

-1.8 N-m +0.40 N-m = -1.4 N-m (clockwise)

This is the only way I was able to get the right answer. However, my first try was using -35Nsin135. Why do I not have to take the component of F in this example?
 
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  • #2
Aren't all the forces in the diagram, tangential?
And how did you arrive at -35Sin135 as the component?
 
  • #3
That's where I was confused. I assumed it wouldn't be tangential because it was on the inside of the wheel.
 
  • #4
Inside of the wheel? I don't really think that matters, it still has to be tangential, even if it's not, again, how did you arrive at -35 sin 135?
 
  • #5
I was thinking that the F of 35N would have to be resolved into components and the only one being effective in producing rotational motion would be F sin θ. I'm pretty sure I'm just mixing up the theory behind torque.
 
  • #6
That ##\theta## in ## \sin (\theta) ## is the angle which the force makes with the radius, in this case I don't thing 135 is that angle, hence I feel we should take it as a tangential force.
 
  • #7
I definitely agree with that. I just have to revisit some of the theory so I'm not confusing concepts.
 

FAQ: Calculating Net Torque on Wheel Axle

How do I calculate net torque on a wheel axle?

To calculate net torque on a wheel axle, you need to know the force applied to the axle and the distance from the center of the wheel to the point where the force is applied. The formula for net torque is T = F x r, where T is the torque, F is the force, and r is the distance.

What units are used to measure torque?

Torque is typically measured in Newton meters (Nm) or foot-pounds (ft-lb).

How does the direction of the force affect the net torque?

The direction of the force affects the direction of the torque. If the force is applied perpendicular to the radius of the wheel, the torque will be in the same direction as the force. If the force is applied at an angle, the torque will be in the direction perpendicular to both the force and the radius.

What is the difference between net torque and moment of force?

Net torque is the total amount of rotational force acting on an object, while moment of force is the tendency of a force to cause an object to rotate around a specific point. In other words, net torque takes into account the direction of the force, while moment of force only considers the magnitude of the force.

How can I use net torque to determine the stability of a rotating object?

The stability of a rotating object is determined by its rotational equilibrium. If the net torque acting on the object is zero, it will remain in rotational equilibrium and be stable. However, if the net torque is not zero, the object will rotate in the direction of the larger torque, making it less stable. By calculating the net torque on an object, you can determine its stability and make adjustments if necessary.

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